Unconvincing complaint raised by the French (6)
I believe the answer is:
feeble
'unconvincing' is the definition.
(I've seen this before)
'complaint raised by the french' is the wordplay.
'complaint' becomes 'beef' (I've seen this before).
'raised by' says the letters should be written in reverse.
'the french' becomes 'le'.
'beef' backwards is 'feeb'.
'feeb'+'le'='FEEBLE'
(Other definitions for feeble that I've seen before include "Weak, lacking strength" , "Wimpish" , "Lacking strength or vigour" , "Weak, debilitated" , "Physically weak or lacking effectiveness" .)